1. Field of the Invention
The present invention relates to a method for directing a down-shift operation for a vehicle with a manual transmission, or in other words, for indicating that the vehicle is running under a condition in which a down-shifting of the manual transmission is needed.
2. Description of Background Information
For vehicles having a manual transmission, various techniques for indicating an appropriate gear position have been proposed so as to promote fuel savings. For instance, Japanese Patent application laid open No. 57-51526 discloses a technique in which an economic range of vehicle running condition is derived from the acceleration or the deceleration of the vehicle which is detected by differentiating a detected value of the vehicle speed. The thus derived economic range is then displayed on a display means in order to send a signal to a driver of the vehicle so that the driver can select the most economic gear position.
However, in the case of the above mentioned conventional technique, there are some problems which occur when the vehicle decelerates during climbing a gradient with the throttle valve fully opened, and when the vehicle accelerates during running on a downhill road with the throttle valve fully closed. Under these conditions, it is very likely to misjudge that the vehicle operation is in the fuel economy range and it fails to indicate the necessary down-shift direction to the driver. Thus the driveability may be lessened when the vehicle is running on an uphill road or a downhill road.